1. Field of the Invention
The present invention relates to a work-machine-lever-support structure for a work vehicle such as various construction equipment including a motor grader, a power shovel, a bulldozer, and the like, or various transportation equipment such as a crane or a transportation vehicle. More particularly, this invention relates to a work-machine-lever-support structure in which the work machine lever can be easily handled, an operator can easily get on and off the vehicle, and the work machine lever is prevented from being operated by mistake when the operator gets on and off the vehicle.
2. Description of the Related Art
One of work vehicles of this type which requires much skill of the operator in operation of the work machine is a motor grader. A motor grader comprises, as shown in FIGS. 1 and 2, for example, a drawbar 2 swingably carried on a front end portion of a vehicle body 1, left and right vertical cylinders 3, 4 for ascending and descending and a cross sliding cylinder 5 connecting the drawbar 2 and the vehicle body 1, a turning circle 6 mounted to the drawbar 2 and turnable by a turning hydraulic motor 7, a blade 9 mounted to a bracket 6a of the turning circle 6 and laterally movable by a shift cylinder 10, and a front wheel 1a which can be laterally leant by a leaning cylinder (not shown).
The above various cylinders and hydraulic motor are operated by an operator in an operation room 11 disposed at a central portion toward a rear end of the vehicle body 1. The motor grader is, as its character requires, designed such that a range of vision from the operation room 11 is as wide as possible. Particularly, in order to reliably allow the operator to look straight at a positioning relationship between the laterally-extending blade 9 obliquely below in front of the operation room 11 and a ground surface with which the blade 9 is in contact, it is necessary to remove as many members as possible that can obstruct the view in front of the operation room 11.
For this purpose, for example, a glass window is detachably mounted at a lower half portion of a front face of the operation room 11, and left and right doors 11a for getting on and off the vehicle are mounted to side walls of the operation room 11 such that the doors 11a can be opened and closed from the front, as shown in FIG. 1. With such structures, the operator can remove the lower half window of the front face and partly open the left and right doors to ensure his/her view in his/her front in the oblique lower direction, if necessary.
Recently, various improvements have been accomplished in this type of vehicle to ensure the view and to facilitate operation of various work machines. One of such improvements is disclosed in Japanese Patent Laid-open Publication No. 6-101247, for example, in which a plurality of operations of the work machine can be carried out by a single operating lever. In this machine, operations of the single operating lever in all directions are converted into electric signals through an electronic controller such as a microcomputer and an electromagnetic flow controlling valve, for example. Then, the above various cylinders and hydraulic motor are controlled and activated based on the electric signals, thereby obtaining a desired ascending or descending position or a desired turning operation of the blade, for example. As compared with a conventional mechanical work machine lever in which the flow rate controlling valve is directly operated through various link mechanisms, a number of the operating levers can be largely reduced and the operating levers take up extremely little space, thereby widening a space for operation in the operation room or making the operation room compact.
There is another example in which an operability of the work machine lever is improved in addition to making the operation room compact, as disclosed in Japanese Patent Laid-open Publication No. 7-173853, for example. The work machine levers disclosed in the above Japanese Patent Laid-open Publication No. 6-101247 is mounted to a floor on left and right sides of a seat. According to the Japanese Patent laid-open Publication No. 7-173853, an end of a shaft is fixed to left and right side walls of a steering post (a steering-wheel-support box) which stands centrally at a front end of the operation room, a free end portion of the shaft extends up to a side of a steering wheel, and a single work machine lever is mounted to the free end portion of the shaft. With such a structure, the operator can easily operate the steering wheel and the work machine levers both in his seated and standing positions, without getting into a special position for either of them, thereby remarkably increasing operability.
With the arrangement of the work machine levers as disclosed in the above Japanese patent Laid-open Publication No. 6-101247, the operator can extremely easily operate the work machine levers in his seated position. However, the operator has to bend himself/herself forward and turn obliquely rearward to operate the work machine levers in his/her standing position, so that the operator can not easily carry out delicate operations, and is extremely fatigued physically.
According to the above Japanese Patent Laid-open Publication No. 7-173853, on the other hand, the operability of the work machine operating lever is remarkably improved as compared with conventional mechanical lever arrangement in which a large number of work machine operating levers are arranged in row on left and right of the steering post, and further as compared with the work machine operating levers disclosed in the above Japanese Patent Laid-open Publication No. 6-101247. However, in order to ensure the view of the operator in the oblique lower direction in front of the operation room, the above-mentioned conventional mechanism still has to be employed for mounting the lower half window at the front face of the operation room and the left and right doors for getting on and off the vehicle.
Apart from mounting of the window, a change of the mounting mechanism of the door is difficult in the present condition, and the operator has to get on and off the operation room through left and right front sides of the operation room. Even if the operating levers can be electrically operated and the number of levers is decreased, from a standpoint of ensuring the view, it is desirable to make the operation room, particularly, a floor face of the operation room, small in size. Consequently, as an area where the operating lever are mounted is made smaller, an area of the floor is decreased, which makes a space for getting on and off the operation room smaller.
With the arrangement of the work machine levers disclosed in the above Japanese Patent Laid-open Publication No. 6-101247, because the work machine levers are disposed on the floor face on left and right of the seat, the operator can promptly enter and going out of the room by opening the door and passing beside the steering wheel. However, because the work machine operating levers as disclosed in the above Japanese Patent Laid-open Publication No. 7-173853 are fixed to a certain position on either side of the steering wheel, the operator's body may often interfere with the work machine operating levers to move the lever by mistake when the operator gets on and off the operation room.